1. Field of the Invention
The present invention relates to a fingerprint recognition sensor and its manufacturing method, and more particularly to a one chip-based finger recognition sensor using a CMOS (Complementary Metal-oxide Semiconductor) sensor and its manufacturing method.
2. Description of the Background Art
Generally, in order for portable information communication instruments such as a mobile phone or a portable computer (that is, a laptop computer) to have a security function by using fingerprints, a very thin fingerprint recognition sensor is required.
FIG. 1 is a schematic view of a fingerprint recognition system in accordance with a conventional art.
As shown in the drawing, a conventional fingerprint recognition system includes an image generator 10 and a sensor-arranged part 20.
The image generator 10 includes a single electrode electro-luminescence device 12 and an A/C power source 14, and the single electrode electro-luminescence device 12 includes a transparent electrode 13, a luminescent layer and a dielectric layer 17.
However, the conventional fingerprint recognition system constructed as described above has a problem that, since the image generator 10 and the sensor-arranged part 20 are separated at a distance to each other, the light coming out of the image generator 10 spreads out to reach the surface of the sensor-arranged part 20 like the arrows as shown in FIG. 1L, rather than traveling straight, resulting in that an optical image of fingerprints is unclear.
In this respect, the longer the image generator 10 is away from the sensor-arranged part 20, the more the light radiating from the image generator 10 is lost, so that the optical image of the fingerprints grows more dim.
In detail, in the conventional fingerprint recognition system, the light coming out of the luminescent layer 15 is radiated in three-dimensional manner. At this time, since the light is reflected on the dielectric layer 17, the light is thus directed to the sensor-arranged part 20. In this respect, the light spreads in a two-dimensional manner, rather than going straight ahead, to reach the surface of the sensor-arranged part 20. And, at this time, the light works on the light reflected on the dielectric layer 17, creating a noise, so that a high contrast image is hardly obtained.
Also, in this case, since the light generated due to the ridge of a fingerprint spreads toward the valley of the fingerprints, it is very difficult to obtain a high-quality fingerprint from a sweat hand of a person.
In addition, the surface of the single electrode electro-luminescence unit 12 is made of a dielectric layer 17. Thus, in case that it is employed as a fingerprint recognition element to be used by numerous persons (i.e., in case of a fingerprint image which has been taken by more than 100 times, which is repeated for a week), as shown in FIG. 2, the surface of the fingerprint recognition element is contaminated by dirt of fingerprints, degrading the finger image.